The present invention relates to the application of atomization technology. More particularly the present invention relates to pressure atomizing a fluid, typically a liquid in order to form a dispersed phase within another liquid which forms a continuous phase. The liquid being atomized is non-Newtonian and immiscible in the continuous phase. In one preferred embodiment the fluid being atomized is subjected to pressure pulsation and is a partially polymerized mixture of one or more monomers.
It has been proposed to atomize and coat monomer droplets in an aqueous medium to form a suspension (Review article E. Vivaldo-Lilma et al., An updated review on suspension polymerization. Ind. Eng. Chem., (36) (1997) of S. Matsumoto et al., A production process for uniform-size polymer particles. J of Chem. Eng. Of Japan, vol. 22, No. 6 1989). It was proposed to use coaxial nozzles and inject the monomer mixture through the inner nozzle and the coating composition through the outer nozzle. The shell of the resulting coated particle is hardened chemically or physically to form a capsule which may be suspended in water and polymerized. Subsequent to polymerization the outer shell is removed from the polymer. The present invention has eliminated an essential feature of the art, as it does not contemplate the formation of a shell about the monomers.
Comparable encapsulation technology is disclosed in U.S. Pat. No. 4,427,794 issued Jan. 24, 1984 assigned to Bayer A. G. Rather than using coaxial nozzles, the patent teaches an encapsulation medium separate from the continuous aqueous phase. As noted above the present invention has eliminated the essential feature of encapsulation required by this reference.
U.S. Pat. No. 5,061,741 issued Oct. 29, 1991, assigned to Mitsubishi Kasei Corporation discloses a method for preparing oil in water type dispersions. The oil is a monomer or monomer mixture which is not polymerized (i.e. a Newtonian liquid to be atomized). The reference fails to teach or suggest the atomization of a non-Newtonian liquid as required by the present invention. Further the reference fails to teach the application of elevated pressure to the oil (monomer) phase. Additionally, the reference teaches the monomer and continuous phase are at relatively low temperatures not exceeding about 30xc2x0 C. A critical feature of the reference is the use of a disperser plate having nozzles in an annular design. The patent teaches away from the present invention in that a disperser plate having an annular layout for the nozzles is not required. The atomizing nozzles may be uniformly distributed over the disperser or orifice plate.
U.S. Pat. No. 3,922,255 issued Nov. 25, 1975 assigned to Rohm and Haas Company teaches atomizing unpolymerized monomers into a continuous water phase. The monomers are not polymerized and therefor are not non-Newtonian. Further the reference fails to teach applying a pressure pulsation to monomer feed to the atomizers. The reference fails to teach the subject matter of the present invention.
There are a series of patents in the name of Timm, assigned to the Dow Chemicals Company which teach dispersing monomer droplets in a continuous phase by subjecting a jet of a monomer mixture to vibratory excitement. This art includes U.S. Pat. Nos. 4,444,961; 4,666,673; and 4,623,706. The references fail to teach atomization of a non-Newtonian liquid. Further the references fail to teach the application of high pressure to the phase to be atomized. Further the flow rates of the Timms references appear to be up to an order of magnitude lower than the flow rates of the present invention.
The present invention seeks to provide a process to pressure atomize non-Newtonian immiscible liquids into a continuous liquid medium.
The present invention provides a process comprising pressure atomizing a non-Newtonian immiscible liquid at a gauge pressure of at least 3 bar, preferably the pressure is subjected to pulsation with a controlled frequency and amplitude, in an amount from 0.01 to 60% volume of a continuous liquid phase, below the free surface of the continuous liquid phase which may be stationary or flowing, contained in a tank, pipe or loop vessel, to produce a dispersion of atomized droplets of the immiscible liquid having at least one controlled average diameter from 0.1 mm to 5 mm.
In a preferred embodiment the droplets are maintained under shear and turbulence conditions insufficient to cause agglomeration or secondary breakup of the atomized droplets.